No unless there are pits in the plums. Yet taste really is the only way your going to know when it's at its peak. I taste all my meads about one a week once in secondary.
Conditioning - 5 gallons Oak Aged Sweet Tart Cherry melomel, 4 1 gallon variations of my Hops Mead.
Bottled - Choujiu (Chinese Rice Wine), Hefe, Godzilla IPA
Kegged - Godzilla IPA
On Deck - Choujiu (Chinese Rice Wine), Cream Soda for the wife n kids, German Style Pilsner with Michigan Hops,
Gone - to many to list.